Lactic Acid Bacteria as A Bio Preservative: Importance and Production

Biopreservation is the method of employing natural microflora and their antimicrobial compounds to extend the storage life and improve the safety of foods. Streptococcus lactis was the first pure strain of lactic acid bacteria which was isolated from milk by Liszt. He named it bacterium lactis. Lactic acid bacteria are gram-positive, acid-tolerant, have low Guanine-Cytosine content and are generally non-sporulating, non-respiring, either spherical cocci or rod-shaped bacilli bacteria that share most of them their metabolic and physiological characteristics. These bacteria are mostly present in decomposing plants and milk products. They have an increased tolerance to acidity. Most species are incapable of respiration and therefore media used for lactic acid bacteria include a carbohydrate source. At the end of carbohydrate fermentation, these bacteria give out lactic acid as a major end product. The review focuses on the process of lactic acid production by lactic acid bacteria and its expanding importance in a variety of disciplines. Keywords: Lactic acid bacteria, bio preservative, food, microflora

Degradation of Poly(ε-caprolactone) by a Thermophilic Community and Brevibacillus thermoruber Strain 7 Isolated from Bulgarian Hot Spring

The continual plastic accumulation in the environment and the hazardous consequences determine the interest in thermophiles as possible effective plastic degraders, due to their unique metabolic mechanisms and change of plastic properties at elevated temperatures. PCL is one of major biodegradable plastics with promising application to replace existing non-biodegradable polymers. Metagenomic analysis of the phylogenetic diversity in plastic contaminated area of Marikostinovo hot spring, Bulgaria revealed a higher number taxonomic groups (11) in the sample enriched without plastic (Marikostinovo community, control sample, MKC-C) than in that enriched in the presence of poly-ε-caprolactone (PCL) (MKC-P), (7). A strong domination of the phylum Proteobacteria was observed for MKC-C, while the dominant phyla in MKC-P were Deinococcus-Thermus and Firmicutes. Among the strains isolated from MKC-P, the highest esterase activity was registered for Brevibacillus thermoruber strain 7 at 55 °C. Its co-cultivation with another isolate resulted in ~10% increase in enzyme activity. During a 28-day biodegradation process, a decrease in PCL molecular weight and weight loss were established resulting in 100% degradation by MKC-P and 63.6% by strain 7. PCL degradation intermediate profiles for MKC-P and pure strain were similar. Broken plastic pieces from PCL surface and formation of a biofilm by MKC-P were observed by SEM, while the pure strain caused significant deformation of PCL probes without biofilm formation.

Comparison of Growth Performance of three Strains of Clarias gariepinus: Hybrid Strain, Selective Breeding Strain and Wild Strain Reared in Concrete Tanks

A comparative study was conducted to investigate the growth performance of three strains of Clarias gariepinus reared in concrete tanks. The experiment was carried out for the period of three weeks. Three strains of Clarias gariepinus which were compared were hybrid strain, selective breeding strain and the pure/wild strain. The experimental fish were randomly assigned to three experimental groups. Each treatment was therefore replicated three times with 60 fry per replicate in concrete tanks. At harvest there was no significant difference among Hybrid strain, Selective breeding strain and wild strain (P˃0.05) in fish’ final body weight (1.83±0.11, 1.178±0.46 and 1.739±0.42). The SGR for hybrid strain, selective breeding strain and wild strains were 12.93 ±0.23, 4.53±0.22and 12.81±0.26. The survival rate for hybrid strain, selective breeding strain and pure strain 70%, 80% and 66.66 %respectively. The was no significant difference (p˃0.05) in FCR (2.12±0.01, 2.12±0.03 and 2.11±0.01) for hybrid strain, selective breeding strain and wild strain respectively. Though the difference was not that significant the pure Clarias gariepinus had the lower FCR as compared to the others. Therefore, this study recommends that hybrid Clarias gariepinus has a good performance as compared to the selective breeding strain and the wild Clarias gariepinus.

Role of biological preparations in increasing yield of pea (Pisum sativum L.) under conditions of steppe Сrimea

The purpose of the research was to study the efficiency of the microbial preparations of polyfunctional action as an element of the pea growing technology under conditions of the steppe Crimea. During the period of the highest activity of nodule formation (flowering phase), pea plants form organs of photosynthetic and symbiotic apparatus. Thus, we did all the necessary observations and measurements. The mass of the above-ground part of the pea plants varied from 14.9 to 27.8 g and exceeded the control variant by 3.1-12.9 g or by 20.8-86.6%. The leaf surface of one plant was from 165.19 to 286.91 cm2. By the number of nodules, the variant, in which seeds were treated with the pure strain 261b (29 pcs.), stood out from the other ones. The process of photosynthesis is functionally associated with nitrogen fixation. So, an increase in these indicators affects plant productivity. The productivity of the plant in the variants with bacterization exceeded the control one by 0.3-1.1 g or 16.7-61.1%. The highest productivity (2.9 g) was observed in the variant with complex preparations – rhizobium technological complex (RTC) 10 seed bacterization. Thus, we found that seeds bacterization can increase the productivity of pea plants by 0.3-1.1 g or 16.7-61.1%; yield – by 0.01-0.17 t/ha or 0.5-9.0%; improve the profitability of pea cultivation by 14.8-29.8%. In 2019, the experiment with the cyano-rhizobium complex bacterization was the most effective. In this case, the yield reached 2.07 t/ha; the yield increase was 0.17 t/ha (LSD05 = 0.17 t/ha).

Comparison of Six Commercial Meat Starter Cultures for the Fermentation of Yellow Mealworm (Tenebrio molitor) Paste

In this study, six commercial meat starters, each consisting of a pure strain of a lactic acid-fermenting bacterium (including Lactococcus lactis, Lactobacillus curvatus, L. farciminis, L. plantarum, L. sakei, and Pediococcus acidilactici), were tested for their ability to ferment a paste produced from the yellow mealworm (Tenebrio molitor). During fermentation, microbial counts, pH, and the bacterial community composition were determined. In addition, UPLC-MS was applied to monitor the consumption of glucose and the production of glutamic (Glu) and aspartic (Asp) acid. All tested starters were able to ferment the mealworm paste, judged by a pH reduction from 6.68 to 4.60–4.95 within 72 h. Illumina amplicon sequencing showed that all starters were able to colonize the substrate efficiently. Moreover, the introduction of the starter cultures led to the disappearance of Bacillus and Clostridium species, which were the dominant microorganisms in un-inoculated samples. Of the six cultures tested, Lactobacillus farciminis was most promising as its application resulted in the largest increase (±25 mg/100 g of paste) in the content of free glutamic and aspartic acid. These amino acids are responsible for the appreciated umami flavour in fermented food products and might stimulate the acceptance of insects and their consumption.